PROJECT SUMMARY Cells communicate with each other via secreted molecules that activate downstream signaling pathways. Many well-studied pathways rely on proteins to act as messengers between cells, but certain lipids also can act as communication mediators. Lipid signaling molecules are stored in latent form as membrane phospholipids, which are broken down by phospholipase A2 enzymes into bioactive lysophospholipids and fatty acids. Lysophospholipid acyltransferases catalyze the reverse reaction in a biochemical pathway known as the Lands Cycle. The Lands Cycle and the lipid mediators it regulates play roles in the mammalian vascular, nervous, immune, and reproductive systems, but interpretation of mammalian studies has been complicated by pleiotropy, redundancy, and technical limitations. Drosophila melanogaster is a premier model system for studying intercellular communication due to its evolutionary conservation but simplicity and short generation time compared to mammals. Prior studies in Drosophila have focused almost exclusively on protein signaling. The research proposed here will investigate lipid signaling in the fly model, using the well-developed genetic tools available, including knockout mutants, tissue specific RNAi, gene overexpression and misexpression. Drosophila Lands Cycle acyltransferases Oys and Nes are required for spermatogenesis. Specific Aim 1 will analyze the mechanism by which Oys and Nes function in the Drosophila testis, specifically examining how they mediate communication between somatic support cells and the germline. Genetic interactions with other pathways that affect levels of lysophospholipids and fatty acids will be assayed. Mass spectrometry will be used to assess changes in lipid levels in oys nes mutants. Specific Aim 2 will investigate Lands Cycle phospholipases A2 and a putative lysophospholipase D in the testis, again using a combination of genetics and mass spectrometry. In a complementary approach, testes will be cultured with chemical enzyme inhibitors. Specific Aim 3 uses the testis system to screen for dominant genetic modifiers of the Lands Cycle, in order to identify regulators and signal response factors of this pathway. It is expected that studying lipid mediated signaling in the Drosophila model will illuminate many fundamental and conserved paradigms, as has been the case for protein signaling, and will help elucidate the roles of bioactive lipids in disease. Aberrant lipid signaling has been implicated in such diverse disorders as metabolic syndrome, atherosclerosis, autoimmunity, asthma, neurological disease, cancer, and infertility. Furthermore, dietary modulation of fatty acid intake has important consequences for health, reproduction, and development, but the mechanisms are not well understood. This research will be conducted with undergraduate and post-baccalaureate students only, on the undergraduate campus of Yeshiva University, thereby strongly addressing the directives of the R15 AREA program: to enhance the research experience of undergraduates, to strengthen the research environment on undergraduate campuses, and to expose undergraduates to developmental model organisms.